It’s one of the most baffling unsolved crimes in FBI history. In 1971, a man, later known as D.B. Cooper, hijacked a Seattle-bound flight, and parachuted out of the airplane with a ransom totaling $200,000. He was never seen again.

Now, as CBS Chicago reports, a retired Indiana construction worker might have cracked the case the FBI never could.

Rick Sherwood served three tours in the U.S. Army during the Vietnam War, earning two Bronze Stars for his code-breaking work.

“I never in my wildest dreams would have ever thought that I would ever use Morse Code, or any kind of code breaking or anything again,” he said.

That changed when Tom Colbert came calling. Colbert, a California-based TV producer, was investigating the D.B. Cooper case, and asked Sherwood to review lines of code in letters sent by D.B. Cooper.